JPS5825020B2 - Iron core and coil structure of rotating electrical machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a means for providing a conductive path from the outer surface of a conductor insulation jacket to a magnetic core in a rotating electrical machine.

In laminated magnetic cores for rotating electrical machines, there is some variation in the tooth dimensions from one laminate to another, and there is variation in the position of the laminates within the core stack.

These irregularities are large enough to result in a somewhat jagged surface of the slot.

The coil used in the machine consists of a winding of porous material impregnated with a thermosetting resin, insulated by an outer jacket consisting of a piece, and molded in a mold while the resin cures to a solid, rigid state.

This makes the outer surface of the coil very smooth and hard, but with some irregularities in its flatness.

When such a coil is in place within the slot, the smooth outer surface of the coil makes physical contact with some of the protruding laminates, leaving a void between the jacket and the other laminates.

Variations in the dimensions of the coil can also create voids or increase the voids mentioned above.

If a portion of the coil edge is smaller than the largest coil edge that will fit into the slot, the gaps remaining between it and the slot wall will be even larger and more numerous than if the coil edge had this maximum dimension. .

In other words, a coil side with a uniform dimension along its entire length at this maximum dimension will fit more snugly into the slot than a smaller coil side.

Actual tolerances on the coil sides may be within a few mils.

For this reason, variations in the dimensions of the coil result in the formation of voids that are equal to or larger than the laminates that make up the core stack.

Electrical plastic materials must be good electrical insulators as well as fairly good conductors of heat.

The epoxy resins made meet this specification.

However, those that meet this condition will harden to a hard state and, once fully hardened, will not soften much when heated again during machine operation.

As a result, the impregnated resin does not soften and flow into the cavity when the coil heats up, as the previously used impregnated asphalt does.

Because the resin material softens with heat and does not flow into the cavity,
The blank space is just 5.

Initially, the outer sheath of the coil is in good electrical contact with the laminate that is furthest into the throat.

This contact brings the sheath and core to approximately the same potential.

However, vibrations caused by machine operation can break this contact, causing a potential difference between the exterior and the core.

This potential difference applies an electric field to the air in the cavity.

This electric field can be large enough to cause a partial discharge from the surface of the coil to the core.

That is, this is a phenomenon called corona or corona discharge.

Operating voltage due to improved resin material. can now be made even higher, resulting in a stronger electric field in the void region, or these new insulators may even strengthen the electric field without increasing the voltage.

When corona discharge occurs, the insulating material often erodes and eventually breaks down.

Are known.

Therefore, the main objective of this invention is to prevent corona in rotating electrical machines.

The air space between the coil sides and the core of a rotating electrical machine also acts as a barrier to heat transfer from the windings to the core laminates.

It is well known that the rating of a machine is limited by its heat dissipation capacity and it is therefore very important to ensure that the heat transfer from the windings to the core is optimal.

Another object of the invention is to prevent corona and improve heat transfer from the windings to the core laminates.

In this invention, a conductive path is provided between the winding coils of a rotating electrical machine and the laminates of the core by disposing a conductive elastic material between the coil sides and the slot walls of the core.

This elastic material is of a type that, when subjected to pressure, deforms to such an extent that it flows into the irregularities between the coil sides and the slot wall, creating a conductive path from the outer insulation jacket of the coil to the core laminates. make.

This material retains its strength, elasticity, conductivity, etc. over the operating life of the machine, under vibration, coolant flow, electric fields, repeated temperature changes, etc., and remains in place between the coil and the core. It has to be something that allows you to be completely absorbed in it.

Silicone resins are well suited for use as materials for creating conductive paths between the coil and the core.

Although silicone resins are inherently good electrical insulators, they are also relatively good thermal conductors.

It is preferable that it is a good conductor of heat in that heat from the coil is transferred to the iron core.

However, this invention fills the resin with fine particles of conductive material, such as carbon powder, lamp soot or mixtures thereof, to make it conductive for corona prevention purposes.

The amount of conductive powder added to the resin should be just enough to provide the desired electrical properties, but not so much that it significantly impairs the physical properties described above.

Canadian Patent No. 932,013 describes a heat transfer material disposed between the coil sides and the slot walls to transfer heat from the outer surface of the coil to the core.

The preferred embodiment of this invention can be considered an improvement on this patent in that the material is also electrically conductive.

However, while thermal conductivity is preferred, it is not essential to the practice of this invention.

Two embodiments of the invention will now be described in detail with reference to the drawings.

In the above and in the following description, the winding of a rotating electric machine is considered to be a very large number of coils interconnected in a suitable circuit form.

Each coil may have one turn or more turns of either a single conductor or multiple parallel strands.

When we talk about the coil side, we are referring to the part of the coil that is placed within the slot in the core.

FIG. 1 shows a portion of a stator of a rotating electrical machine, such as a large generator.

It has a laminated core 10 and a winding 11.

The core consists of a stack of laminated plates 12 with a plurality of axially oriented slots 13, and the winding consists of a plurality of coils 14.
, 15, 16, etc., and its coil side 17.1
8 are arranged in two different slots, and an end coil 19 projects from the iron core in the axial direction.

Each coil is positioned with one side at the bottom of one slot and the other side at the top of another slot, as shown for sides 17 and 18 of coil 14.

The arrangement of the core and coil shown in Figure 1 has a coil width of approximately 1
The pole pitch is conventional, having a plurality of equally spaced slots with a conventional distributed winding.

This arrangement is often found on the primary side of an AC motor or on the armature of an AC generator.

The invention described below is in no way limited to this particular arrangement of cores and coils, or to any other arrangement.

In FIG. 2, a portion of the coil side 17 or 18 is shown as being composed of a plurality of conductor strands 20, which are insulated from each other, as indicated by 21.

The entire strand is enclosed within a jacket consisting of a number of superimposed insulation layers 22, 23 and an outer armor jacket 24.

The insulation of the strands may be a coating with bonded glass filaments.

After the strands are formed into a coil with the desired number of turns and shape, the insulation jacket and outer jacket are applied.

The insulating layer is typically a resin-bonded mica tape;
The sheath can be a semiconductor tape or one or more layers of paint, ie, a material with controlled resistance.

The tape can be several mils thick and can be applied in multiple layers depending on the voltage it is to withstand.

Each layer is applied as tightly and evenly smooth as possible, after which the resin in the tape is cured by heat and pressure to provide the desired insulation properties.

Even with very careful application of the tape and curing of the resin with the coil side in the pressure mold, 35 and 3 in Figure 3.
6, there is some variation in the width of the coil sides as well as the flatness of their radial surfaces.

These variations are typically so great that the coil edge itself leaves a void between itself and the slot wall, or makes voids caused by irregularities in the slot wall more noticeable.

When fully cured, the resin bonded material becomes very hard and tough and does not soften significantly when reheated.

As a result, the faces 25 and 26 of the coil form a somewhat irregular and non-yielding interface with the irregular faces of the stampings forming the slot walls.

The hard side of the coil, like a conventional bituminous compound, softens when reheated by machine operation, filling the voids defined by these irregularities and creating electrical contact with the core laminates. It does not deform to the extent that it maintains its properties.

Initially, the semiconductor package is in good electrical contact with the core laminates, so that the sheath and slot walls are held at approximately the same potential.

However, vibrations from machine operation disrupt this contact and create a potential difference, which strengthens the electric field relative to the air in the cavity.

This increase in electric field can be large enough to cause a corona in the cavity, ie, a partial discharge from the outer jacket 24 to the core 10.

Furthermore, even after repeated heating, the irregularities between the coil and core remain a barrier to heat transfer from the coil to the core laminates.

Since the insulation jacket retains its shape, it can only make physical contact with one protruding laminate.
Leave a void or small air pocket between the jacket and the recessed laminate.

Therefore, the heat generated in the conductor is transferred to the core mainly through the protruding laminated plates that are in contact with the jacket.

This does not provide optimal cooling and does not result in the best use of the conductor as a current carrier.

The materials for the jackets 22, 23, 24 are selected to have good electrical and thermal properties.

Therefore, as long as predetermined fairly good transfer conditions are obtained at the interface between the outer jacket and the core, heat can be sufficiently transferred from the conductor to the core.

In one embodiment of the invention, the radial surfaces 25, 26 of each coil side 11.degree. Cover with 28°C.

Even without layers 27, 28, the coil sides will have a fairly close fit or clearance fit in the slot, and with these layers, an interference fit in the slot.

Note that the structural body in FIG. 2 is also referred to as a conductor rod.

FIG. 3 shows an exaggerated illustration of the coil sides at their final resting place within the slot.

When the coil side is press-fitted into the throat, the interfering protruding laminated plate 29.30 transfers the material of the layer 28 to the surface 26 of the coil side.
The space 31 left between the retracted laminate plate 33°34
．． 32.

In other words, the compressive force exerted on the material by some of the laminates causes the material to flow over the other laminates and cause the material to flow over other laminates where it would otherwise remain between some of the laminates and the jacket. Enter the void.

The initial thickness of layers 27 and 28 is such that, once deformed, most of the laminates are in contact with the deformed material, so that this material is conductive from the coil sheath to the laminates approximately aligned with the core. Just enough to form a bridge.

This bridge is electrically conductive, ie has a controlled resistance, allowing charge on the sheath to flow to the core.

Preferably, it also has thermal conductivity.

Materials found to be suitable for making layers 27 and 28 include finely divided conductive material, in proportions that impart a controlled resistance to the material but do not appreciably alter the properties of the resin. For example, room temperature vulcanizing silicone resins filled with carbon powder and/or lamp soot.

The semiconductor material referred to in this invention is a conductive material with a controlled resistance value, that is, the resistance value is low enough that the material easily conducts the charge on the outer sheath of the coil to the laminate plates of the iron core. A material whose resistance is so great that the edges of the plates are not electrically connected together in the form of eddy current paths.

The filled elastic material has a thixotropic consistency so that it can be applied as a thin layer to surfaces such as those shown at 25 or 26.

In forming the layers 27,28, a strip of filled resin is placed on each side 25, 26 and the strips are formed into a uniform layer 27,28 by placing the coil sides in the mold. and hold in this state until the resin has hardened enough to hold its shape.

A piece of damp paper can be placed between the material and the mold to accelerate the curing of the resin.

The layer thickness may be on the order of 5 to 20 mils.

The filled silicone resin cures to a permanently flexible state.

They do not harden, crack, or dry out over time.

It is a strong, sturdy, unbreakable electrical conductor with controlled resistance, and a relatively good conductor of heat.

It bonds well to other materials and is resistant to aging, electric fields, chemical attack and high temperatures.

Because these materials have adhesion to the jacket of the coil, as well as flexibility and toughness, they form layer 27.
28 is the preferred material.

These materials are displaced from a region of a tighter fit to a region of a looser fit between the jacket and the slot wall when the coil sides are pushed into the slot.

To facilitate insertion of the coil side into the slot, its outer surface can be coated with a thin film of petroleum grease and the slot walls can be sprayed with liquid fluorocarbon.

The fleece and fluorocarbon act as a lubricant at the coil-slot interface.

In FIG. 2, layer 27 is shown divided into three strips 27A, 27B, 270 arranged along the length of the coil sides.

For electrical applications, it is not necessarily necessary to cover the entire area as shown at 21, and even better results may be obtained if the entire area is not covered.

However, from the standpoint of heat transfer, it is preferable to cover the entire area.

As a result, the strip 27A is made electrically and thermally conductive,
The remaining strips 27B and 270 can be made to be only thermally conductive.

In other words, strip 27A is the filled silicone resin described above and strips 27B and 270 are the unfilled thermally conductive silicone resin described in Canadian Patent No. 932,013, cited above.

In order to easily transfer the heat generated in the coil to the core, the entire coil should be made of 27.
It is preferable to cover it as shown in .

When forming layer 21 on strips 27A, 27B and 270,
Three very narrow strips of resin are placed along the face of the coil and then molded into wider flat strips by the method previously described.

Layer 28 can also be formed in strips, as is illustrated for layer 21.

Since the resin material is effectively crushed between the sheath on the coil side and the slot wall, this brings a substantial area of the sheath into electrical as well as thermal contact with a substantial area of the slot wall.

Although it is preferred that the material fills all cavities and is in full contact with all surfaces, this is not essential.

In most cases, the total contact area between the core and coil surfaces is 7
A strip somewhat larger than 5 will provide adequate heat transfer, and a strip of this area will provide adequate discharge paths to keep the surfaces at approximately the same potential to minimize corona. .

Even without the use of layers 27 and 28 of elastic material, the coil edges would have a fairly close fit, i.e., no gap, in their slots; with these layers, there would be an interference fit in the slots. I mentioned it before.

With an interference fit, when the coil side is pressed into its slot, the protruding laminate will force some of the elastic material of layers 21 and 28 into the space between the outer jacket of the coil side and the recessed laminate. Forced flow to.

Additionally, to facilitate insertion of each coil side into the slot, the outer surfaces of layers 27 and 28 can be coated with a thin film of petroleum grease, and the slot walls can be sprayed with liquid fluorocarbon.
It was also mentioned earlier that this grease and fluorocarbon act as a lubricant at the interface between the coil and the slot.

However, if the coil side is a particularly tight interference fit within the slot, it has been found that it is very difficult to insert the coil side into the slot by normal hand.

If a press machine is available, it can be used to press the coil sides into the slots.

However, press machines are not always available.

Figures 4 and 5 show another embodiment of the invention in which the elastic material is distributed on the coil sides in such a way that they are more easily deformed when the coil sides are inserted into the slots.

This makes it easier to insert the coil sides into the slots by hand, ie, without using a press.

In these figures, layers 121 and 128 of elastic material are layer 1
27, a number of ridges 3 along the coil.
Shaped from 1 to 40.

These edges may be generally triangular in cross-section.

For example, FIG. 5 shows triangles for edges 37 and 38, whereas triangles 39 and 40 have rounded peaks and valleys.

In practice, edges having the overall shape shown at 39 and 40 are used.

This is because it is easier to use elastic material in this shape.

Layers of elastic material 127 and 128 are applied as follows.

First, a thin layer of elastic material is applied across the coil sides.

Immediately thereafter, a comb-shaped sparge member having generally triangular teeth is pulled along the sides of the coil so that the teeth spread the elastic material into a plurality of generally triangular strips or ridges along and over the sides of the coil. Shape it into a shape.

The strips can also be formed to extend laterally rather than along the sides of the coil.

However, since the elastic material hardens quickly, it is faster and easier to form strips along the length of the coil sides.

It may be desirable to combine application and dispersion operations.

For this purpose, the application device and the dispersing element can simply be combined into one unit.

It has been found that it is actually easier to insert the coil edges into the slots when the elastic material is distributed in the form of ridges.

This is to be expected regardless of the shape of the ridge; if there is enough material on the ridge, the ridge will deform to fill the approximate space between the coil edge and the slot wall.

For example, the covering of an edge in the form of a regular triangle corresponds to a uniform layer with a thickness equal to half the height of this edge.

The longitudinal or lateral edges of the coil sides are not the only way to distribute the elastic material.

The elastic material may be formed into individual drops or pyramid-shaped peaks.

In each case, the filled elastic material provides a good conductive path for electrical discharge as well as heat transfer.

This is because the material is coupled to the coil and is deformed against the slot wall, so that a large portion of the wall is in contact with the material.

It is to be expected that some voids will remain, but these voids are still in the middle of the conductive material and do not significantly impede electrical or thermal conductivity.

In Figures 2 and 4, the semiconductor material is shown only on the radial side of the coil, but in order to prevent corona from occurring in the coil as much as possible, the non-radial side resting on the bottom of the slot. The material can also be coated with either a layer or a ridge.

In some cases, it may be desirable to apply material to the other, non-radial side of the coil as well.

The air is also subjected to ionizing effects in the area where the coil emerges from the slot.

Ionization in these areas can be minimized by extending the semiconductor coating far enough out from the core to provide a safe, gentle voltage gradient.

Such an extension is shown at 41 in FIG.

The strand coil sides shown in FIGS. 2 and 4 may be one coil side of a multi-turn coil or a single turn strand coil.

A coil suitable for use in this invention may consist of a single turn of suitably shaped, sturdy conductor.

When this invention is applied to a water turbine generator, the coil is usually a solid conductor with one turn, that is, the coil sides 11 and 18 are slender conductors.

The one-turn coil is insulated by a jacket, in much the same manner as applied to the bare wire coil sides shown in Figures 2 and 4, and has a solid hard side which enters the slot with the rod. .

Materials that have been found suitable for layers 27, 28, 127, 128 include room temperature vulcanization (RTV) silicone resins.

This type of resin is typically a thermal conductor as well as an electrical insulator.

Therefore, to make it electrically conductive, the material is filled with fine particles of graphite and/or lamp soot.

Examples of suitable silicone resins include RTV-108 and 0RTV from General Electric Company.
It is sold under the name -5120.

The former is an unfilled thermally conductive silicone resin, and the latter is a filled electrically and thermally conductive silicone resin.

The amount of filler added is about 1000 to so, ooooo
- Just enough to give the material an electrical resistance value in the range of ohms square, preferably about 4,000 ohms/square.

If the resistance value is controlled within this range, the material will become
It is electrically conductive enough to easily transfer the charge on the outer sheath of the coil to the core, and non-conductive to the extent that eddy current paths are not formed between the laminates of the core.

The resistance value of the material is of the same order of magnitude as the resistance value of the outer sheath of the coil.

Such materials are known in this field as semiconductor materials.

The amount of filler added is small enough that the physical and chemical properties of the material are not appreciably altered and that these properties and electrical resistance values are maintained over the life of the machine.

In addition, when the iron core and conductor structure of a rotating electric machine are configured as shown in FIG. is partially provided on the side of the conductor rod, the amount of material used for the strip 27A is small, and if silicone resin and carbon powder etc. are dispersed and mixed as this material, the amount of material Since the amount is small, the resistance value tends to be uniform, and therefore the price is low.

In addition, elastomers such as silicone resins in which carbon powder is dispersed have lower elasticity than silicone resins alone, and are more likely to deteriorate in elasticity. Strips 27B and 270 are provided adjacent to strip 27A, and these strips are made of an insulating and elastic material such as silicone resin. Even when press-fitting into the slot of the laminated core as shown in the figure, not all of the press-fitting force is applied to the strip 27A;
Since it is also applied to the strip 27A, the force applied to the strip 27A is actually small as a component force, so the strip 27A will not be torn during press-fitting.

Moreover, the conductor rod press-fitted into this slot is constantly subjected to external forces such as the vibrations of the rotating electric machine and the thermal expansion and contraction of the laminated iron core (due to the thermal expansion and contraction of the laminated iron core).
, 270 (thereby, this external deformation stress is alleviated, so no deformation force is constantly applied to the strip 27A, and therefore, the elastic deterioration of the strip 27A occurs rapidly over time) This has the effect of maintaining good electrical contact between the conductor rod and the laminated iron core for a long time.

This invention can take the following embodiments in relation to the description of claim 1.

b) The adhesion process involves applying a relatively thin longitudinal strip of room temperature vulcanizable semiconductive silicone resin having an electrical resistance value within the range of about 1000 to about 1,000 ohms/square to at least one radial surface of the sheath. Consisting of molding pieces.

(a) The bonding process involves forming a plurality of triangular strips of room temperature vulcanizable semiconductive silicone resin having electrical resistance values in the range of about 1000 to so,oooo-ohm squares on at least one radial surface of the sheath. Consisting of forming pieces.

9. The adhesion step forms a plurality of droplets of room temperature vulcanizable semiconductive silicone resin having electrical resistance values in the range of about 1000 to 000-ohm squares on at least one radial surface of the sheath. consisting of doing.

→ In items A) to C) above, after the bonding process but before the press-fitting process, apply a lubricant to the outer surface of the silicone resin and apply the lubricant to the slot wall.

This invention is described in claim 2 (in connection with this, the following embodiments may be taken).

e) The semiconductor material is a thermally conductive elastic material in which fine particles of a conductive material are dispersed.

f) The semiconductor material is filled with finely divided graphite and/or lamp soot in such an amount that the filled resin has an electrical resistance value in the range of approximately 1000 to 1000 ohms/square. It must be a silicone resin for room temperature vulcanization.

g) the semiconductor material is in the form of at least one thin layer bonded to the outer jacket;

h) The semiconductor material is in the form of a generally triangular shaped strip bonded to the outer jacket.

) Semiconductor material is in the form of individual peaks joined together by an outer jacket.

[Brief explanation of drawings]

1 is a perspective view of a part of a large number of coils and an iron core of a rotating electric machine, FIG. 2 is a perspective view of a part of the coil, and FIG. 3 is a plan view of the inside of the slot of the structure shown in FIG. 1; FIG. 4 is a perspective view of a portion of the coil showing the elastic material distributed as strips or ridges along one coil side. 5 is a partial end view showing in particular detail the strip of elastic material of the coil of FIG. 4; FIG. Explanation of main symbols, 10... Iron core, 11...
...Winding, 12... Laminate, 13...
Slot, 14, 15゜16... Coil, 1
7, 18...Coil side, 22゜23...
・Insulation jacket, 24...exterior jacket,
27.28... Layer of semiconductor material.

Claims (1)

[Claims] 1 consisting of a laminated core provided with a slot for receiving a conductor bar, the conductor bar having a bonding end that reaches the core after the conductor bar is inserted, and each conductor bar having at least one a conductor on at least one side of the conductor rod, and an outer layer with an inner insulating layer and a semiconductive hard outer jacket around the outer circumference, the outer layer being on at least one side of the conductor rod and an outer layer of the outer jacket. at least one strip of resilient, semi-conductive material coupled to at least one strip of resilient, non-conductive material adjacent to the strip of semi-conductive material; the outer layer covering the sides of the conductor bar and having a thickness sufficient to fit snugly when the conductor bar is inserted into the slot. Iron core and conductor structures for rotating electrical machines.